The present invention relates generally to purified and isolated proteins and DNA molecules; to methods of screening for receptors; and to methods of treatment of ovarian and breast cancer, and more particularly to a purified and isolated BRCA1 protein cleavage products; and to gene therapy methods using the BRCA1 gene and the BRCA2 gene in the treatment of breast and ovarian cancer; and to methods for identifying the receptors of the BRCA1 protein and the BRCA2 protein.
The human breast and ovarian cancer susceptibility gene BRCA1 is mutated in the germline and lost in tumor tissue in hereditary breast and ovarian cancer (Hall et al., 1990, Science 250, 1684-1689; Miki et al., 1995 Science 266, 66-71; Smith et al., 1992; Cornelius et al., 1995, The Breast Cancer Linkage Consortium. Genes Chrom Cancer 13: 203-210).
Despite much excitement with the discovery of BRCA1, mutations were only found in the germline which accounts for only a small minority of breast cancers (Futreal et al., 1994, Science 266, 120-121). In addition, BRCA1 was found to be expressed at the same levels in normal individuals and sporadic breast cancers (Miki et al., 1994, Science 266, 66-71). Thus, the initial excitement over BRCA1 was followed by great disappointment.
The BRCA2 breast and ovarian cancer susceptibility gene has also recently been identified. (Wooster, R., et al., Nature 379: 789-792, 1995).
To date all tumor suppressors discovered encode proteins which are not secreted. Steeg, (review article), 1996, Nature Genetics 12:223. To treat the cancer associated with these tumor suppressors requires expressing the normal protein in the affected cell. Thus, these cancers have not been treatable with extracellular administration of the normal protein encoded by the tumor suppressor gene. For this reason, gene therapy has been proposed as the most likely means to supply a normal functional tumor suppressor protein.
This invention significantly modifies the state of the BRCA art by providing that the BRCAs are secreted and thus are amenable to direct therapy or prevention by contacting the BRCA receptor on the cell surface. In addition, the invention provides that BRCA1 is indeed underexpressed in sporadic breast cancer and thus sporadic breast cancer is amendable to therapy and prevention by correcting the BRCA deficiency. Other embodiments are also provided.